The present invention relates to a light-emitting device reflecting light generated in a light-emitting layer by a first electrode to extract the light from a second electrode side, a method of manufacturing the light-emitting device, and a display unit using the light-emitting device.
In recent years, as one of flat panel displays, an organic light-emitting display using an organic light-emitting device has become a focus of attention. The organic light-emitting display is of a self-luminous type, so it is considered that the organic light-emitting display has advantages of a wide viewing angle, low power consumption and adequate response to high-definition high-speed video signals. Therefore, the development of the organic light-emitting displays toward practical utilization has been proceeding.
As the organic light-emitting device, for example, a laminate including a first electrode, an organic layer including a light-emitting layer, and a second electrode with a TFT (thin film transistor), a planarizing layer and the like in between in order on a substrate is known. Light generated in the light-emitting layer may be extracted from the substrate side or the second electrode side.
As an electrode where light is extracted, in many cases, a transparent electrode made of an electrically conductive material with transparency such as a compound including indium (In), tin (Sn), oxygen (O), indium tin oxide (ITO) and the like is used. Various structures of the transparent electrode have previously been proposed. For example, in order to prevent an increase in cost due to an increase in the thickness of an ITO film, a transparent electrode including a laminate of a metal thin film made of silver (Ag) or the like and a high refractive index film made of zinc oxide (ZnO) or the like has been proposed (for example, refer to Japanese Unexamined Patent Application Publication No. 2002-334792). In the transparent electrode, the high refractive index film has a thickness of 5 nm to 350 nm, and the metal thin film has a thickness of 1 nm to 50 nm, so the high refractive index film is relatively thicker than the metal thin film, thereby the transparency of the transparent electrode is increased, and reflection by a surface of the metal thin film can be reduced by the high refractive index film.
In many cases, as an electrode where light is not extracted, various metal electrodes are used. For example, when light is extracted from the second electrode side, the first electrode as an anode is made of, for example, a metal such as chromium (Cr). Conventionally, for example, a first electrode with two-layer structure including a metallic material layer made of chromium and a buffer thin film layer made of an oxide including chromium has been proposed, thereby the surface roughness of chromium of the metallic material layer is reduced by the buffer thin film layer (for example, refer to Japanese Unexamined Patent Application Publication No. 2002-216976).
When light is extracted from the second electrode side, light generated in the light-emitting layer may be directly extracted through the second electrode, or may be reflected by the first electrode once to be emitted through the second electrode. Conventionally, the first electrode is made of chromium or the like, so there is a problem that the light absorptance of the first electrode is large, thereby a loss of light reflected by the first electrode to be extracted is large. The light absorptance of the first electrode has a large influence on the organic light-emitting device, so when the light-emitting efficiency is lower, a larger amount of current is required in order to obtain the same intensity. An increase in the amount of drive current has a large influence on the life of the organic light-emitting device which is extremely important for practical use of the organic light-emitting device.
Therefore, for example, it is considered that the first electrode is made of silver (Ag) with the highest reflectance among metals or an alloy including silver. However, silver has properties such that its reactivity is extremely high, it is difficult to be processed, and its adhesion is low. Therefore, in order to achieve a chemically stable first electrode with high reflectance through making full use of advantages of silver, the structure and the manufacturing process of the first electrode are susceptible to further improvement.